Originally Posted by
peteq
The bear is an example of Contra-rotating propellors - twin propellors on a common axis with an opposing spin.
Counter rotating propellors are multi engine aircraft where the left and right engines turn opposite.
I believe all of the Piper twins (Navajo, Semenole etc) were counter rotating. The Cessnas aren't.
Another classic example of something messed up is the counter-rotating props on a P-38. Both were critical engines, the instability enchanced maneuverability. I did a research paper on this plane in college, and I still to this day feel it's one of the most under-rated fighters of WWII. But that's a different topic entirely.
Hope some of these answers help out. Props aren't Jets in almost every aspect of their aerodynamics, systems, etc.. Basic skillsets can be applied, but in the end we fly them differently.
Never hurts to learn